Synthesis and photoluminescence properties of Ba3(PO4)2:Eu3+/2+ phosphors

Single-phase phosphors of Ba3–хEu2х/3(PO4)2 (x = 0.01, 0.02) were obtained for the first time using solid-phase synthesis. These phosphors are isostructural to the palmierite mineral. The self-reduction of Eu3+ to Eu2+ in the Ba3(PO4)2 host was observed in air at high temperature. The dependence of luminescence intensity on temperature was studied over a broad range of 80–500 K. The luminescence intensity of Eu3+ is significantly depends on temperature and decreases as the temperature increases, while Eu2+ emission remains stable between 150–500 K. Eu3+ ions incorporated into the polyhedra of the M1 sites of the Ba3(PO4)2 structure demonstrated improved thermal stability compared to Eu3+ ions in the polyhedra of the M2 sites. Photoluminescence spectra, when excited at 395 nm, consist of intense bands at 585 nm and 610 nm, typical for Eu3+ cations. When excited at 330 nm, the luminescence spectra display a broad band centered at 425 nm, typical for Eu2+ cations. The resulting orange-red phosphors have potential applications in solid-state lighting.